The present invention relates to a metal laminate gasket with half beads for sealing around a hole.
In a metal laminate gasket, it is common to provide a bead on a metal plate around a hole to be sealed. When the bead is compressed, the bead provides surface pressure thereat to seal around the hole.
The bead may have a full bead, i.e. projecting outwardly with two sides, or a half bead, i.e. projecting outwardly with one side. The full bead is formed of a projection or corrugations, and provides high surface pressure. In the other hand, the half bead includes a side wall to form a stepped portion.
When the half bead is compared with the full bead, the half bead is superior to the full bead in recovering ability and provides surface pressure with low tightening force. Thus, the half bead is used as auxiliary sealing means for sealing, for example around a periphery of a gasket.
Recently, in order to make a high power engine, the engine or a part of the engine has been made of an aluminum alloy to have light weight. Since the aluminum alloy is not rigid, if high tightening pressure is applied to the engine made of the aluminum alloy, such engine deforms. Similarly, if high surface pressure is formed by the full bead of the gasket installed in the engine made of the aluminum alloy, the portion of the engine abutting against the full bead may deform.
Since the half bead does not form high surface pressure when the half bead is compressed, the half bead has been used more frequently. Namely, the half bead is used for sealing around an exhaust hole for a manifold gasket, or a water hole or an oil hole for a cylinder head gasket.
In the half bead, the surface pressure is generally formed at bending portions thereof. Namely, one half bead has two portions forming the surface pressure. Thus, the half bead can not provide large sealing area.
In order to provide a large sealing area, in Japanese Utility Model Publication No. 63-84461 published on Jun. 2, 1988, two plates have different half beads to be laterally spaced apart from each other. Although the wide sealing area is formed by the two half beads, surface pressure is not formed even.
In Japanese Utility Model Publication No. 2-61170 published on May 7, 1990, a gasket is formed of a plate with a half bead and a heat insulating material, such as ceramics. Thus, heat from a cylinder head does not escape through a manifold.
In a conventional gasket with half beads, a wide and constant surface pressure is not generally obtained, and no proposal therefor has been made.
Accordingly, one object of the invention is to provide a metal laminate gasket with half beads, which can provide wide and ideal surface pressure.
Another object of the invention is to provide a metal laminate gasket as stated above, wherein surface pressure and width thereof can be easily adjusted.
A further object of the invention is to provide a metal laminate gasket as stated above, which can be easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.